FIELD OF THE INVENTION
The present invention relates generally to orthopedic supports for the wrist and to the management and treatment of wrist sprain, carpal tunnel syndrome and tendinitis of the wrist and forearm and hand. More specifically the present invention represents a new and innovative approach to carpal tunnel problems. The present invention simultaneously applies independent anterior midline compression and anterior midline torsion to the distal ends of the radius, ulna and lateral walls of the carpal bones, to relax the flexor retinaculum (the transverse and volar carpal ligaments) and reverse posterior to anterior (dorsal to palmer) prolapse of the carpal tunnel. In so doing, this device relieves pressure on the median nerve, carpal ligaments and other soft tissue structures of the wrist while allowing full and unrestricted motion of the wrist, hand and fingers.
"Carpal Tunnel Syndrome", as well as many cases of tendinitis and other cumulative trauma disorders (CTD's) of the wrist and forearm, result from repeated trauma to the tendons and soft tissue structures that pass through the wrist. Excessive pressure on the carpal tunnel contents, including the flexor tendons and bursa, results in abnormal function, weakness, inflammation, pain, numbness and ultimately in injury to the median nerve.
The carpal tunnel is composed of a bony arch formed by the radius, ulna and carpal bones and closed by the flexor retinaculum which anchors the base of the arch together.
The flexor retinaculum is a thick, unyielding ligamentous band that crosses the groove on the palmer surface of the carpal bones. It is composed of the palmer (volar) carpal ligament and transverse (anterior annular) carpal ligament. The palmer carpal ligament is attached medially and laterally to the styloid processes of the radius and ulna. The transverse carpal ligament is attached medially to the pisiform bone and the hamulus of the hamate, and laterally to the tuberosity of the scaphoid and palmer surface of the ridge of the greater multangular (trapezium). The fibers of these ligaments merge at the distal end of palmer and proximal end of the transverse ligament. Together with the carpal bones, they form a tunnel through which pass the deep flexor tendons and median nerve.
The median nerve lies in the carpal tunnel adjacent the flexor retinaculum and between it and the flexor tendons and their bursa. The carpal tunnel is barely adequate to accommodate these structures and it is generally felt that any narrowing of the diameter of the tunnel or decrease in the diameter to contents ratio, causes injury to the median nerve by repeatedly pressing it against the relatively unyieldable retinaculum. Repetitive forceful movement, in particular extension movements of the hand, are thought to repeatedly traumatize the median nerve in this manner.
A study of FIGS. 1-3 reveals that prolapse or collapse which narrows the tunnel in such a way as to compress the internal structures against the flexor retinaculum, occurs primarily in posterior (dorsal) to anterior (palmer) direction. Posterior to anterior displacement would result in decreasing the posterior to anterior diameter of the tunnel, makes the flexor retinaculum more taut and compresses the flexor tendons and median nerve against the taut retinaculum. Midline movement of the bony structures or anterior to posterior movement of the carpals would have the opposite effect however, i.e., relaxing the flexor retinaculum and increasing the posterior to anterior diameter of the tunnel.
Current medical treatment of carpal tunnel syndrome consists of rest, restriction from traumatizing activities, limiting movement with restrictive splints, anti-inflammatory medication and cortisone injections. In advanced cases surgery is used to transect and spread the transverse carpal ligament to allow more room for the contents of the carpal tunnel, i.e., an increase in the diameter to contents ratio. Some form of wrist support or splint is normally used in the early stages of treatment. They are used in an attempt to delay progression of the condition or as an adjunct to some other treatment in an effort to lessen the pain and aid in the return to normal function. Subsequent to surgery, wrist splints are frequently used to support the wrist and aid in recovery. Thus it is important that a presurgical device be provided which corrects the condition or prevents further development and/or progression of the condition.
Many types of orthoses, referred to as braces, supports and splinting devices, have been proposed to address this problem, e.g., shown in Des. Pat. No. 339,866 and U.S. Pat. No. 4,883,073. Such supports typically include metal or some type of reinforcing part to restrict or limit movement, e.g., shown in U.S. Pat. Nos. 4,047,250, 4,883,073 and 5,267,943. These devices usually include a part that fits around the thumb and hand such as a thumb loop, or some other means of securing the device to the arm and hand to prevent slippage.
Devices like those referenced above, either partially or totally limit or inhibit flexion and/or extension movements of the wrist and abduction and adduction movements are also inhibited. Dexterity of the hand, wrist and fingers is also generally compromised. In theory, these supports limit the stress by limiting the movement.
U.S. Pat. Nos. 4,628,918 and 5,372,575, represent yet another type of orthosis which is intended to compress musculoskeletal structures to achieve a therapeutic effect. U.S. Pat. Nos. 4,048,991, uses circumferential compression in an attempt to lock the wrist and carpal bones in a so called neutral position. U.S. Pat. No. 4,966,137, utilizes straight line compression to squeeze the distal forearm, i.e. the radius and ulna in an attempt to alter the carpal tunnel. Still other types of compressive devices, such as U.S. Pat. Nos. 4,991,234 and 5,478,306, represent simple devices which have long been used for general support. Still another type of device represented by U.S. Pat. Nos. 5,468,220 and 5,256,136, attempts to stretch the flexor retinaculum.
The above referenced devices fail to account for the dynamics of bone and joint movement and the structural dynamics of the carpal tunnel. Forces applied to the carpal area of the wrist must be directed at relaxing the flexor retinaculum and increasing the anterior to posterior diameter of the carpal tunnel, i.e. reversing posterior to anterior prolapse. These actions allow more unrestricted room for the contents of the carpal tunnel.
Bones and joints are known to generally resist compressive forces. By contrast torsional forces are known to move bones and joints to the point that, if excessive, will injure the joint and supporting tissues. Therefore a simple compression of the bones and joints of the wrist, whether straight line or circumferential, would be resisted and would not significantly alter the posterior to anterior prolapse of the carpal bones or relax the flexor retinaculum. To achieve such conditions the device should provide compressive forces on both sides of the carpal tunnel along with anterior midline torsion forces thereon so that each side of the carpal tunnel is simultaneously compressed and torsioned toward the anterior midline. Such forces must be in excess of any forces acting on the dorsal side of the tunnel so as to increase the diameter of the carpal tunnel in an anterior to posterior direction and reverse prolapse.
Thus, a device which relaxes the flexor retinaculum and reverses carpal prolapse would provide maximum benefits. The above referenced devices do not simultaneously apply bilateral anterior midline compression forces along with anterior midline torsional forces on the carpal tunnel, these forces necessary to alter the bony and soft tissue structures of the wrist. Thus, the desired actions on the carpal tunnel are not performed.
Current methods of treatment alone or in combination have met with varying degrees of success. Current methods of splinting or supporting the wrist, which are widely used in early cases, are inadequate and fail to significantly alter the progression of the carpal problematic conditions. Even when "successfully" treated by current methods, carpal tunnel problems often return as soon as the patient returns to work or resumes the activities that precipitated the onset of symptoms. With carpal tunnel surgery the patient is frequently left with varying degrees of residual dysfunction, and a lifetime of continuing problems.
Carpal Tunnel Syndrome and its corollary conditions account for an increasing cost in terms of workers compensation claims, lost productivity and settlements. These conditions have now surpassed back injury as the No. 1 cause of workers compensation costs. Since wrist splints and supports are often the earliest form of treatment and prevention, it is imperative that a type of support be developed that insures a high probability of success, has preventative value, is inexpensive and simple to use without requiring costly doctors visits and fitting fees, and allows for quick return to normal and full function of the affected person.